The present invention relates to a tire inflation pressure monitor. More specifically, the present invention pertains to a transmitter that transmits data, especially data relating to tire inflation pressure, to a receiver attached to an associated vehicle body. The present invention also relates to an external controller that externally controls the operation of the transmitter.
Wireless tire inflation pressure monitors that permit the tire inflation pressure of vehicle tires to be checked from the passenger compartment are known. The known tire inflation pressure monitor includes transmitters that are respectively attached to the wheels and a receiver located in the body of the vehicle. Each transmitter measures the tire inflation pressure of a corresponding tire and transmits data, which includes the measured pressure, by radio waves. The receiver receives the transmitted data and a display in front of the driver displays the information.
Each transmitter transmits data relating to the tire inflation pressure of a corresponding tire to one receiver. The receiver has to distinguish which transmitter the data is from. Therefore, each transmitter has its own ID code and transmits tire inflation pressure data and ID data, which include the ID code. Therefore, the receiver recognizes the transmitter that transmitted the tire inflation pressure data, based on the ID data.
The ID codes of the transmitters in the tires must be registered in the receiver in advance so that the receiver can associate a given set of tire inflation pressure with a transmitter. Therefore, when a new tire is attached to the vehicle or when the position of a tire relative to the vehicle is changed, the ID codes of the transmitters in the tires are initially registered in the receiver. In detail, the receiver includes an initialization switch that is operated when the ID codes are initially registered. When the switch is operated, the ID codes that are included in the data transmitted by the transmitters are initially registered in the receiver.
Since each transmitter is powered by a built-in battery, each transmitter stops operation when the battery is dead. However, the transmitters are attached to the wheels inside the tires. When the batteries are replaced, the tires must be removed from the wheels, which is troublesome. Therefore, generally, data transmission from each transmitter is carried out intermittently at predetermined intervals (for example, ten-minute intervals). As a result, the transmitters can operate for a relatively long period without replacing the batteries.
The initial registration of the ID codes of the transmitters is not complete until all the transmitters in the tires finish data transmission after the initialization switch of the receiver is operated. However, as already mentioned, each transmitter performs data transmission at, for example, ten-minute intervals, which are relatively long intervals. Therefore, it takes ten minutes at the longest to complete the initial registration after the initialization switch is operated. If the interval time of data transmission of each transmitter is shortened to reduce the time spent for the initial registration, the life of the battery of each transmitter is shortened.
Wireless communication is performed between each transmitter and the receiver. The output of radio waves is regulated in each nation by different laws. When the transmitters manufactured in one country are shipped to another country, the radio wave output by the transmitters may not comply with the communication laws of the country that manufactures the transmitters, although it complies with the laws of the destination country. In that case, operation of the manufactured transmitters must be stopped in the manufacturer""s country. Also, in the country to which the transmitters are shipped, the transmitters must be started. However, the transmitters are designed on the assumption that the batteries will not require replacement. To stop and restart the operation of the manufactured transmitters, the batteries have to be detached and reattached, which is difficult and troublesome.
A typical transmitter integrally includes a valve stem. When the transmitter is attached to a wheel, the valve stem projects outward from the wheel. An antenna coil is located close to the valve stem. The antenna coil is coated with insulating material. The transmitter wirelessly transmits data through the valve stem and the antenna coil by wireless.
To improve the efficiency of emitting radio waves from the antenna coil, it is preferred to attach the antenna coil to a part as close as possible to the distal end of the valve stem. However, since the valve stem functions as an inlet for air into the tire, an optimally placed antenna may be an obstacle to filling the tire with air.
Therefore, the antenna coil is actually attached near the proximal end of the valve stem. However, various wheel designs exist in the market, and some wheels do not permit the valve stem to project from the wheels. When the transmitters are attached to such wheels, the antenna coil cannot emit radio wave efficiently. Therefore, the shapes of wheels to which the transmitters can be attached are limited.
An objective of the present invention is to provide a transmitter for tire inflation pressure monitors that can readily stop or start data transmission without the need for troublesome procedures.
Another objective of the present invention is to provide a transmitter for tire inflation pressure monitors that can improve the efficiency of transmitting radio waves.
A further objective of the present invention is to provide an external controller that is suitable for controlling the operation of a transmitter.
To achieve the above objectives, the present invention provides a transmitter for performing wireless transmission of data concerning vehicle tire inflation pressure. The transmitter includes a transmission antenna, a pressure sensor for measuring the tire inflation pressure, a transmission circuit for sending data that includes data representing the measured tire inflation pressure to the antenna for wireless transmission, a controller for controlling the pressure sensor and the transmission circuit, and a signal generation circuit. The signal generation circuit is connected to the antenna, generates a trigger signal for activating or deactivating data transmission from the transmission circuit based on a particular signal received through the antenna, and sends the trigger signal to the controller.
The present invention further provides a transmitter for performing wireless transmission of data concerning tire inflation pressure of a tire supported by a vehicle wheel. The transmitter is structured as follows. A main body is located inside the tire. A valve stem extends from the main body through the wheel. A removable cap is attached to the distal end of the valve stem. An antenna coil is embedded in the cap. A pressure sensor is located in the main body to measure the tire inflation pressure. A transmission circuit is located in the main body. The transmission circuit sends data that includes data representing the measured tire inflation pressure to the antenna coil through the valve stem for wireless transmission.
The present invention further provides an external controller for controlling a wheel transmitter that performs wireless transmission of data concerning tire inflation pressure of a vehicle tire. The external controller includes a wireless transmission antenna, an operation switch, an oscillator, which generates a trigger signal for activating or deactivating the transmission of data from the wheel transmitter when the operation switch is turned on, and a transmission circuit, which demodulates and sends the generated trigger signal to the transmission antenna.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.